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A Multiwavelength Study of a Sample of Texas Radio Survey Steep Spectrum Sources


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Title: A Multiwavelength Study of a Sample of Texas Radio Survey Steep Spectrum Sources

A Multiwavelength Study of a Sample of Texas
Radio Survey Steep Spectrum Sources
  • Ray A. Lucas (STScI), Neal Miller (NRAO/JHU),
    Anton M. Koekemoer (STScI), Jeff Van Duyne (Yale
    Univ.), Kenneth C. Chambers (IfA-Univ. of

  • THANKS Many thanks to the NSF, NVO (all of us),
    and the Jansky Fellowship program (Neal Miller)!
    Also, thanks to Pat Crane, our VLA contact for
    his assistance in setting up the observations
    (evening up times on source, etc.) in 1990.
    Thanks also to numerous other VLA staff who made
    the AOC and site visit and observing run a good
    one. Finally, RAL thanks Gerry for her patience,
    and Peter Barthel for advice, a lift, and for
    introducing him to the pleasures of dining at the
    famed Eagle Guest Ranch in Datil, New Mexico!

How many of you have old unreduced, unpublished
  • This is a story about redemption
  • Our VLA observations made in Spring 1990.
  • Later VLA FIRST survey similar sensitivity, but
    our A-array resolution is still much better!
  • First NVO Summer School in September 2004 served
    as the occasion for our Texas Survey VLA sample
    to be revisited

A bit about the Texas Survey
  • Texas Interferometer used, sources observed at
    365 MHz, complete to flux density of 250 mJy
  • Covered area 35.5 lt declination lt 71.5 deg
    66,841 sources in published (1996) catalog
    (Douglas, J.N. et al., AJ 111, 1945)
  • An earlier version (Douglas et al., 1980, Univ.
    of Texas Publications, Publications on Astronomy,
    No. 17) comprised one declination strip, and
    other versions circulated before final 1996
  • We used a contemporary (ca. 1989) version of the
    catalog to derive our original sample in 1989.

At the 2004 NVO Summer School
  • We each had to pick predefined projects, or come
    up with others of our own devising and work on
    them either individually or in groups for 1.5
    intense days.
  • Projects were then presented. What follows next
    was part of our presentation at the time

Steep Spectrum Texas Survey Radio Sources - Good
Indicators of Distant Galaxy Clusters? NVO
Summer School 2004
  • Ray Lucas, David Rohde, Takayuki Tamura, and Jeff
    Van Duyne

  • Original VLA proposal (Lucas Chambers, 1989)
    Selected 71 steep spectrum Texas Interferometer
    Radio Sources from 1989 catalog
  • Complete sample 1 full Schmidt SRC-J
    high-latitude sky survey plate of radio sources,
    6 degrees on a side.
  • Field chosen was combination of deepest digitized
    Schmidt plate material for optical IDs and
    highest galactic latitude to avoid galactic plane
  • Original goal Investigate nature of sources and
    potential of digitized Schmidt plates and the
    Texas Survey as discovery material for
    medium-to-high-z galaxy clusters

  • SRC-J plate reached limiting mag of J22, and CCD
    images of all individual targets would have taken
    significant time plate astrometry was also
    well-known automated
  • From our original visual inspection of digitized
    plate material for the VLA proposal (1989)
  • Apparent magnitudes consistent with 3C 4C
    objects at 0.4 lt z lt 0.8 from plates, several
    had peculiar optical morphology consistent with
    powerful radio sources at these redshifts or
  • 52 of 71 objects had faint optical ID on
    digitized Schmidt plate material 3C273 also a
    brighter source in the sample inclusion of 3C273
    was not by design.

  • Only 1 object was moderately bright source at
    relatively low-z
  • 18 of 71 sources on the plate visually appeared
    to be distant rich clusters
  • 15 of 71 sources might be called obviously
  • 3 of 71 sources visually resembled cD galaxies
    with large halos
  • Original goal also included catalog of radio
    morphologies, spectral indexes, optical IDs look
    at statistical properties, e.g. ID fraction,
    largest angular size distribution, spectral index
    distribution, and positional accuracy, etc.

  • On this basis, a VLA proposal was submitted and
    accepted (Lucas Chambers, 1989), and VLA
    A-array Snapshots (20cm, 1485 MHz fluxes) were
    obtained for the full sample (Lucas Chambers,
    1990, unpublished)
  • Life (work personal lives) then intervened in
    big ways for the investigators, and resumption of
    the project was delayed for a long time!
  • But newer multiwavelength surveys and NVO
    developments (and NVO Summer School) provided new
    opportunities to pick it up again!
  • Can still test idea of using digitized sky survey
    as well as Sloan, if desired Sloan u,g,r,i,z
    bandpass coverage is a big plus at similar

  • Wanted to take advantage of newly-released Sloan
    coverage (SDSS DR2) which is slightly deeper(??)
    (g,r22.2) than SRC-J plate and has ugriz 5-band
    color information and some spectroscopy.
  • Wanted to make use of other surveys and data in
    IR, x-ray, and radio from sources such as 2MASS,
    ROSAT, XMM, Chandra, and VLA FIRST, etc. since
    our VLA snapshot data were unreduced.
  • Wanted to use new VO capabilities to enable a
    more multiwavelength exploration and discovery
    space which can also still relate back to
    original idea of using digitized Schmidt plates
    and can test for validity of original method.

  • NVO Summer School 2004
  • Initial NVO Summer School idea was to take
    radio positions, do SIAP extractions of them at
    wide variety of wavelengths, from x-ray to IR and
    radio, and then compare them to seek evidence of
    whether these sources were a link to finding
    medium-to-high-z galaxy clusters.
  • Radio sources might be cD galaxies or AGN in
    clusters hot x-ray gas in IGM might also be
    clues to clusters.
  • Blank IDs could also be dust-obscured or high-z
    AGN. (UV, optical, infrared dropouts the key.)
  • Stellar sources could be quasars.

  • Sloan images would show optical appearance of
    possible clusters 2MASS images could possibly
    show high-z galaxies in IR where no optical ID
    was found. (At least that was the initial hope.)
  • Wanted to feed SIAP extractions done by Jeff into
    web form done by David, and Takayuki was doing
    more science analysis, cross-referencing these
    and other x-ray and radio observations and
    catalogs, etc. using Topcat. Each discussed his
    part in this. The devil was in the details, but
    we did have some images and they displayed on a
    (now defunct) web page, and we had some (now
    missing) cross-correlation plots of larger radio
    vs x-ray catalogs!
  • (My apologies to David and Jeff and Takayuki)

  • Wouldnt stake our scientific futures on this,
    but from a very quick visual analysis of Sloan
    images at the Summer School
  • 3-4 appeared to be associated with cD or similar
    galaxies in nearer clusters
  • 11 appeared to be in richer cluster-like areas
    and 9 more in poorer areas or possible loose
  • 18 had no immediately obvious optical ID within
    0.2 arcmin, so were interesting candidates for
    higher-z objects in IR, radio, x-ray, etc

Some more about the present NVO-funded study
  • VLA A-array images maps made! (Thanks to Neal
    Miller, and the NRAO Jansky Fellowships!)
  • Again, using Sloan optical data and SRC-J
  • Use 2Mass for IR if nothing deeper, but may be
    too shallow to place useful limits on any really
    high-z non-detections will search again for any
    new IR observations (NVO Footprint server,
    DataScope, etc.)
  • Will also search again for any new x-ray
    observations, etc. using same tools as above.

  • Ultimate aim to create a NVO registry with the
    source list, dynamic database of multiwavelength
    images (FITS, jpeg, etc.), and/or links for SIAP
    catalog extractions, including our new/old VLA
    A-array images, plus a dynamic catalog database
    of the major multiwavelength properties of the
    objects in the sample. Publication of the source
    list could enable on-the-fly harvesting of new
  • SQL should enable query of objects properties in
    the database could put into VOTable format.
  • Catalog database should enable use of VOTable and
    VOPlot, etc. for comparison and plotting of
    various properties in the sample versus other
    properties, and hopefully versus other catalogs

Current Status
  • Initial versions of all VLA A-array maps now
    finished. (May revisit some to see if some
    non-detections benefit from alternative
    processing to emphasize sensitivity over
    resolution. Also cross checking these against VLA
    FIRST survey.)
  • A few sources (4 spurious and 5 weak) from our
    original list (based on a pre-publication catalog
    of 1989) were removed or flagged in the
    published (Douglas et al.,1996) Texas catalog.
  • A few other static optical, etc. images
    extracted still need to set up links for dynamic
    SIAP extractions of user-specified field size,

  • Still have to set up database and NVO registry
  • Still have to set up SQL queries
  • Once those are done, we (and ultimately others)
    can use them to explore more
  • The current survey is large in some sense (the
    area of an entire 6x6 degree Schmidt plate), but
    small in some others (60-70 sources versus
    thousands in Texas Survey).
  • Can possibly help serve as a template for larger
    radio samples linking to other multiwavelength
    surveys covering larger areas can then more
    easily compare our results to work of others who
    have used larger radio samples, as well

Other issues which may benefit from VO and other
tools, etc.
  • For those sources which appear to have no optical
    counterpart, we can try other more rigorous
    methods than simply looking visually (e.g. VO
    SExtractor, etc.) 2MASS probably too shallow for
    real substantive IR limits for dropouts on blank
  • Search for new, deeper IR observations from time
    to time
  • Request new, deeper optical and IR observations

A Gallery of a Few New VLA and Related Images
Some new VLA images (1)1219023 AGN in
NOTE Images are not at same scale!
1219023 Sloan Spectrum (1a)for brighter
sources z0.1258
Sloan spectra available for redshifts etc.
of brighter sources
Sloan data may allow us to derive phot-zs for
some fainter sources
Radio power 4.7E24 W/Hz, typical for source of
this type at this redshift (WMAP cosmology
synchroton spectral index)
More new VLA images (2)1220023 v. faint
ID in Cluster?
1220023 Maybe in cluster, (2a)but not the one
you may think!
  • Radio morphology of this sort is usually
    associated with very bright elliptical galaxies
  • Can be a signpost for clusters (Hot gas in
    clusters is needed to confine the radio source.)
  • Should be associated with 1 or 2 brightest
    optical objects in cluster, but it is not
    associated with one of those kinds in the
    possible foreground cluster
  • Probably associated with v. faint optical objects
    that may be the brightest optically in a much
    more distant cluster? (Foreground objects are too
    bright to be associated with the radio source)

More new VLA images (3)1229-021 QSO,
X-Ray source
More new VLA images (4)1247-012 cD
Galaxy in A1620?
1247-012 VLA A-Array vs (4a)VLA FIRST -
Effects of Resolution vs Sensitivity
VLA A-Array 5min Snapshot
More new VLA images (5)1250029 4C02.34
More new VLA images (6)1236004 only
part of it?
More new VLA images (6a)1236004 The rest
of it?
More new VLA images (7)1234018 More
double lobes
1234018 Resolution vs (7a) Sensitivity
comparable noise
(158 uJy/beam)
(151 uJy/beam)
VLA A-Array 5min Snapshot
(Base contour level rms noise level for all
More new VLA images (8)1245-025 FR1,
NAT?, Cluster
1245-025 Emission lobes (8a)swept back
(motion through gas)
(Flux 0.121 Jy)
(Flux 0.126 Jy)
VLA-A over Sloan optical image
1245-025 Why a cluster? (8b)
  • FR1 with lobes of emission swept back by relative
    motion within intracluster gas likely a
  • Degree of sweeping indicated by names Wide Angle
    Tail (WAT) and Narrow Angle Tail (NAT)
    sweeping is large in 1245-025, hence possible
  • z0.182 (SDSS spec.) power 1E25 W/Hz, so very
    powerful FR1. (Many sources at this power would
    have pair of bright lobes instead of bright jet
    with fainter lobes You would usually see FR2
    sources at these power levels.) Transitional?

1245-025 A Mystery (8c)
Jets dont seem to originate within the big E
galaxy as they should, but radio contours are
coincident with E. Still, radio flux and
morphology fit with E galaxy as host. A z0.2
is maximum consistent with the data, and a big
E at zlt0.2 would be very visible in SDSS.
So, why the misalignment?
More new VLA images (9) 1249-010 X-Ray
1249-010 VLA-A vs (9a) VLA FIRST
again z0.358
VLA-A array 5 minute snapshot
Higher resolution less flux
Lower resolution more flux
VLA FIRST recovers 50 more flux due to lower
resolution here.
Source power is 9E25 W/Hz v. strong. Typical of
big double lobes.
Other VO-related issues, etc.
  • Dont want to re-invent the wheel!
  • Other NRAO and VLA VO-related work on astrometry,
  • Other new tools wed like to see (but again,
    dont want to reinvent the wheel!)
  • Physical size per angular size and cosmology
  • (perhaps based on Google calculator and
  • into Aladin?)
  • Multiwavelength graphical flux
  • tool showing flux across the electromagnetic
  • Graphical phot-z tool?

  • VLA Morphologies 43 sources double-lobed
    3-4/43 show distinct core 21/43 show diffuse
    emission 9 sources are resolved, and 9 are point
    sources 7 apparent non-detections (being
    investigated) 4 spurious, from 1989 list.
  • Our VLA-A array 5-minute snapshots and VLA FIRST
    are definitely complementary surveys, despite
    their similarities, as are others (Sloan, etc.)
  • Other science conclusions and implications for
    galaxy formation, etc.?
  • Much science and real VO work yet to be done! It
    is very much a work in progress!
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